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PostPosted: 22 Sep 2017, 20:59 
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Here are some progress photos of a bass reflex speaker enclosure that I am putting together to be used with the Audio Nirvana Classic 8 full range speaker driver.

Attachment:
Birch-Plywood-for-Speaker-Box.jpg

The plywood is 3/4 inch (19 mm) thick multiplex (11 ply) birch. The price is $40 (Canadian) per 4' x 8' (1.2 x 2.4 m) sheet (purchased from Rona). The birch plywood is fairly void free, but the outer veneers are virtually paper thin. This birch plywood is not the superior quality of a true Baltic birch plywood, but it is good quality and a very good value at this price.

Attachment:
Butt-Joint-Birch-Plywood-Speaker-Box.jpg

To construct the bass reflex speaker enclosure, the plywood pieces were simply butted together, glued and well clamped.

Attachment:
Gluing-Birch-Plywood-Speaker-Box.jpg

For the damping material an R12 insulation was used and is held in place using 12 mm staples at about 4 inch spacing. This seems like it will work really well as an acoustic dampening material.

Attachment:
Acoustic-Insulation-Bass-Reflex-Speaker-Box.jpg


Attachment:
Acoustic-Insulation-Bass-Reflex-Speaker-Box-2.jpg

And gluing the final piece of birch plywood to finish up the bass reflex speaker box.

Attachment:
Final-Gluing-Birch-Plywood-Speaker-Box.jpg


I was pretty happy with the end result of the speaker box. There was a little excess to trim off with a flush trim router bit on one end. The ports has a very small roundover. T-nuts are used for the driver.

Attachment:
Birch-Plywood-Bass-Reflex-Speaker-Boxes.jpg


For the finish I am planning on using a dark "Ebony" Minwax oil stain. I am thinking a dark finish will help to hide the plywood laminations on the edges. Before staining I'll apply Minwax prestain wood conditioner to prevent blotching. Two coats of ebony stain. Then I buff with ultra fine steel wool #0000. To finish I am thinking a coat of a polyurethane. I should get that done this weekend and I'll post photos.

Cheers


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PostPosted: 26 Sep 2017, 19:58 
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The photo below shows the birch plywood enclosures after staining with Minwax Ebony. I think it turned out pretty good. When I opened up my can of polyurethane it had already hardened. At the store I picked up a tin of "Wipe on Poly". I'll try a coat or two of that before I finish up the speakers. The back panel will have insulation damping as well. None on the front baffle.

Attachment:
Stained-Birch-Plywood-Bass-Reflex-Speaker-Boxes.jpg


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PostPosted: 28 Sep 2017, 17:05 
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excellent workmanship.


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PostPosted: 26 Dec 2017, 10:44 
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Merry Christmas everyone.

After having had to put this project (and others) on pause for some time in order to attend to some home repairs and renovations, I finally got a chance to resume work over this past week to finish up this speaker project. Stain was applied to the cabinets in the fall and for the final finish I used 2 coats of wipe-on poly. This product works real well with no streak so I don't imagine I will be using thick brush on poly anymore.

See the attached photo of the finished speakers in the workshop.
Attachment:
AN-Classic-8-Bass-Reflex.jpg

I used a dual binding post speaker plates on the lower rear of the speaker boxes. The top speaker binding posts are wired directly to the Audio Nirvana Classic 8" full range speaker driver. The bottom speaker binding posts lead to a passive BSC (Baffle Step Compensation) circuit. This way the listener has the option of hooking the fullrange speaker driver to the amp or to employ the use of the passive baffle step compensation circuit. This idea is from the Fostex FE127E bass reflex speaker project by Rabbitz. I'll post most details of the BSC once I've had a chance to crop the photos.

So far I have the speakers in the basement rec. room sitting inverted on my back loaded horn speakers. Not an ideal room or setup, but so far I'm liking the bass response I am hearing. The "bookshelf" speakers are tall enough I think these may work best sitting right on the floor and tilted back aimed at the listening position.

I should get a chance to move these upstairs in the next day or so and a listening report will follow.

Cheers


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PostPosted: 09 Jan 2018, 21:45 
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Attached below is a photo of the baffle step compensation network. Using the dual binding post speaker plates
gives the listener the option of hooking the fullrange speaker driver to the amp or alternatively to use the passive baffle step compensation circuit.

Attachment:
Speaker-Plate-BSC.jpg


Here are the speakers sitting inverted on a pair of back loaded horn speakers. Not the ideal setup, but ok to break in the drivers. Tonight they will be moving upstairs into the main listening room. I will try the bookshelf speakers on stands and also on the floor tilted back towards the listening position. I'll have comments about the sound after I get some good listening upstairs.

Attachment:
Audio-Nirvana-Classic-8-Bass-Reflex.jpg


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